1. Technical Field
The embodiments herein generally relate to Digital Video Broadcasting, and, more particularly, to Digital Video Broadcasting—Handheld (DVB-H) receivers with low power consumption.
2. Description of the Related Art
In order to implement a service level in a network for a customer, service requirements are typically expressed in measurable quality of service (QoS) metrics. For wireless networks, jitter, bandwidth, noise, and fading are some of the deciding QoS metrics. For example, frame error rate (FER) is a link-layer metric while fading and the resulting bit error rate (BER) are Physical layer metrics (PHY metrics). PHY metrics may include power, distance, signal-to-noise ratio (SNR), signal-to-noise-and-interference ratio (SNIR), BER, and/or packet error rate (PER). BER is the number of erroneous bits received divided by the total number of bits transmitted. PER is the number of video packets in error compared to the total number of video packets.
Coverage maps are designed to indicate the service areas of radio communication transmitting stations. Typically a coverage map will indicate the area within which the user can expect to obtain good reception of the service in question using standard equipment under normal operating conditions. Additionally, the map may also separately denote supplementary service areas where good reception may be obtained but other stations may be stronger, or where reception may be variable but the service may still be usable. Antenna diversity is a transmission technique in which the information-carrying signal is transmitted along different propagation paths. This can be achieved by using multiple receiver antennas (e.g., diversity reception) and/or by using multiple transmitting antennas (e.g., transmit diversity). A diversity combining circuit combines or selects the signals from the receiver antennas to constitute an improved quality signal.
One method of diversity combining is maximal-ratio combining (MRC), in which the signals from each channel are added together, the gain of each channel is made proportional to the root mean square (RMS) signal level and inversely proportional to the mean square noise level in that channel, and different proportionality constants are used for each channel. DVB-H is a technical specification for bringing broadcast services to handheld receivers, terrestrial television (TV), portable TVs, mobile phones and other such mobile terminals. In DVB-H device systems, diversity receivers are used to improve the carrier-to-noise (C/N) performance and to provide diversity gain (e.g., by about 3 to 9 dB) in static to slow varying channel conditions and/or Doppler frequency (e.g., by twice) in mobile channel condition. In addition, they suppress part of the ingress noise and short echoes problems, thus offering significant reception performance improvement with portable and mobile reception in places where a single receiver would not function.
FIG. 1 illustrates a typical DVB-H diversity receiver 100 having two identical single receivers 102 and 104, with corresponding antennas 106 and 108. The single receivers 102 and 104 each include tuners 110 and 112, and baseband digital receivers 114 and 116, as shown in FIG. 1. A combining block may maximize the SNR after the combination. The power consumption of the diversity receiver 100 with two antennas 106 and 108 will thus be approximately twice the power consumption of the corresponding single receiver. In power hungry applications like DVB-H, low power consumption is critical to the success of diversity receivers in the mobile TV market. Further, if the channel condition in one of the channels in the diversity receiver is poor, it may actually result in degraded performance after MRC combining as compared to the performance of the single receiver. Accordingly, there remains a need for a scheme for low-power consumption operation of DVB-H receivers without performance degradations.